Maternal hypothyroidism reduces the expression of the kisspeptin/Kiss1r system in the maternal-fetal interface of rats

Alterations of circulating and placental levels of kisspeptin have been associated with gestational diseases. However, there are still no studies on the placental and decidual expression of Kiss1 and its receptor Kiss1r in maternal hypothyroidism, which is the aim of this work. We demonstrate that the fetoplacental restriction caused by hypothyroidism in rats is associated with a reduction in the Kiss1r expression and reduced Kiss1 and Kiss1r mRNA levels in the decidua and/or placenta. This demonstrate that fetoplacental restriction in hypothyroid rats is linked with a suppression of the kisspeptin/Kiss1r system at the maternal-fetal interface.     

Plasma kisspeptin levels are elevated in cord blood and present sexual dimorphism in the adult population: relation with leptin, gonadotropins and anthropometrical data

Kisspeptin, the product of the hypothalamic KISS1 gene, is a main regulator of the hypothalamic-pituitary-gonadal axis and could be a link between metabolism and reproduction through its interaction with leptin. Kisspeptin could be involved in gonadotropin regulation and responsive to leptin levels from the first stages of life, exhibiting, as does leptin, sexual dimorphism. To test our hypothesis, we have analyzed plasma kisspeptin levels and their possible relationship with gonadotropins and leptin in a cohort composed of newborns (n = 86) and adults (n = 55). Plasma kisspeptin, gonadotropin and leptin levels were measured by RIA and multiplexed bead immunoassays, respectively. We have built a multivariate linear regression model (analyzing kisspeptin and LH separately as dependent variables) by stepwise analysis, incorporating the variables that had shown significant correlation in the univariate analysis. Cord blood samples exhibited high kisspeptin levels 127.01(113-141.02 pmol/l), but these were not sexually dimorphic. The adult population exhibited sexual dimorphism (3.72(2.95-4.49) vs. 1.77(1.23-2.31) pmol/l women vs. men, p < 0.05). Leptin levels showed sexual dimorphism in cord blood samples and also in the adult population. Furthermore, there was a significant interaction between LH and kisspeptin levels and kisspeptin was negatively correlated with age. The high kisspeptin levels observed in cord blood, with no sexual dimorphism, suggest a placental source. The sexual dimorphism exhibited in adulthood supports the notion that there are different sources and/or differential kisspeptin regulation between men and women.     

Interplay of KNDy and nNOS neurons: A new possible mechanism of GnRH secretion in the adult brain

Reproduction in mammals is favoured when there is sufficient energy available to permit the survival of offspring. Neuronal nitric oxide synthase expressing neurons produce nitric oxide in the proximity of the gonadotropin-releasing hormone neurons in the preoptic region. nNOS neurons are an integral part of the neuronal network controlling ovarian cyclicity and ovulation. Nitric oxide can directly regulate the activity of the GnRH neurons and play a vital role neuroendocrine axis. Kisspeptin neurons are essential for the GnRH pulse and surge generation. The anteroventral periventricular nucleus (AVPV), kisspeptin neurons are essential for GnRH surge generation. KNDy neurons are present in the hypothalamus's arcuate nucleus (ARC), co-express NKB and dynorphin, essential for GnRH pulse generation. Kisspeptin-neurokinin B-dynorphin (KNDy) neuroendocrine molecules of the hypothalamus are key components in the central control of GnRH secretion. The hypothalamic neurons kisspeptin, KNDy, nitric oxide synthase (NOS), and other mediators such as leptin, adiponectin, and ghrelin, play an active role in attaining puberty. Kisspeptin signalling is mediated by NOS, which further results in the secretion of GnRH. Neuronal nitric oxide is critical for attaining puberty, but its direct role in adult GnRH secretion is poorly understood. This review mainly focuses on the role of nNOS and its interplay with KNDy neurons in the hormonal regulation of reproduction.     

Leptin and reproductive function

Adipose tissue plays a dynamic role in whole-body energy homeostasis by acting as an endocrine organ. Collective evidence indicates a strong link between neural influences and adipocyte expression and secretion of leptin. Developmental changes in these relationships are considered important for pubertal transition in reproductive function. Leptin augments secretion of gonadotropin hormones, which are essential for initiation and maintenance of normal reproductive function, by acting centrally at the hypothalamus to regulate gonadotropin-releasing hormone (GnRH) neuronal activity and secretion. The effects of leptin on GnRH are mediated through interneuronal pathways involving neuropeptide-Y, proopiomelanocortin and kisspeptin. Increased infertility associated with diet induced obesity or central leptin resistance are likely mediated through the kisspeptin-GnRH pathway. Furthermore, Leptin regulates reproductive function by altering the sensitivity of the pituitary gland to GnRH and acting at the ovary to regulate follicular and luteal steroidogenesis. Thus leptin serves as a putative signal that links metabolic status with the reproductive axis. The intent of this review is to examine the biological role of leptin with energy metabolism, and reproduction.     

Formation of Kiss1R/GPER Heterocomplexes Negatively Regulates Kiss1R-mediated Signalling through Limiting Receptor Cell Surface Expression

Kisspeptin receptor (Kiss1R) is an important receptor that plays central regulatory roles in reproduction by regulating hormone release in the hypothalamus. We hypothesize that the formation of heterocomplexes between Kiss1R and other hypothalamus G protein-coupled receptors (GPCRs) affects their cellular signaling. Through screening of potential interactions between Kiss1R and hypothalamus GPCRs, we identified G protein-coupled estrogen receptor (GPER) as one interaction partner of Kiss1R. Based on the recognised function of kisspeptin and estrogen in regulating the reproductive system, we investigated the Kiss1R/GPER heterocomplex in more detail and revealed that complex formation significantly reduced Kiss1R-mediated signaling. GPER did not directly antagonize Kiss1R conformational changes upon ligand binding, but it rather reduced the cell surface expression of Kiss1R. These results therefore demonstrate a regulatory mechanism of hypothalamic hormone receptors via receptor cooperation in the reproductive system and modulation of receptor sensitivity.     

Design and synthesis of fluorescent probes for GPR54

Kisspeptins are neuropeptides that induce the secretion of gonadotropin-releasing hormone via the activation of the cognate receptor, G-protein coupled receptor 54 (GPR54). The kisspeptin–GPR54 axis is associated with the onset of puberty and the maintenance of the reproductive system. In this study, several fluorescent probes have been designed and synthesized for rat GPR54 through the modification of the N-terminus of rat kisspeptins to allow for the visualization of the expression and localization of kisspeptin receptor(s) in living cells and native tissues. The tetramethylrhodamine (TMR) and rhodamine green (RG)-labeled kisspeptins exhibited good binding and agonistic activities towards GPR54, and the results of the application studies demonstrated that these fluorescent probes could be used effectively for the detection of GPR54 receptors in flow cytometry and confocal microscopy experiments.     

西红花酸治疗DHT诱导的PCOS小鼠的机制研究

目的:观察西红花酸对双氢睾酮(Dihydrotestosterone,DHT)诱导的多囊卵巢综合症(Polycystic ovarian syndrome,PCOS)小鼠的疗效并探讨其作用机制。方法:妊娠15-18天给予孕鼠皮下注射DHT诱导子代雌鼠PCOS模型。待子鼠8周龄后,随机选择一半数量的PCOS小鼠连续4周西红花酸灌胃,作为西红花酸给药组(n=18)。给药期间检测体重和动情周期,待小鼠16周龄左右,通过眼球取血后处死,取出下丘脑、卵巢。采用HE染色观察卵巢组织的病理改变;ELISA试剂盒检测血清中雌二醇(Estradiol,E2)、睾酮(Testosterone,T)、孕酮(Progesterone,P4)、促黄体生成素(Luteinizing hormone,LH)、卵泡刺激素(Follicle-stimulating hormone,FSH);采用免疫组化、Western blot和实时荧光定量PCR法检测下丘脑的前腹侧视旁核(Anteroventral periventricular,AVPV)、弓状核(Arcuate,ARC)的kisspeptin以及视前区(Preoptic area,POA)里Gn RH的表达水平。结果:与对照组相比,PCOS小鼠卵巢与体重的比值上升了22.56%±6.77%,动情周期延长,卵巢内出现大的空泡,闭锁卵泡数量增加了138.74%±33.22%,窦状卵泡、成熟窦状卵泡和黄体数量分别减少了38.80%±4.69%、56.35%±7.32%和63.77%±7.25%,血清中E2、P4和FSH水平分别降低了40.99%±2.69%、56.91%±5.25%、和38.80%±4.69%,而T、LH水平分别升高了43.23%±4.70%和148.46%±28.16%,下丘脑中AVPV中kisspeptin神经元表达减少,ARC中kisspeptin神经元表达增多,POA中Gn RH神经元减少,而以上情况能够被西红花酸改善。结论:西红花酸分别通过促进和抑制下丘脑AVPV核和ARC核团的kisspeptin表达改善PCOS的病理变化。     

Molecular interaction between kisspeptin decapeptide analogs and a lipid membrane

Kisspeptin-10 is the C-terminal decapeptide amide of kisspeptin, an endogenous ligand for GPR54, and exhibits the same binding and agonist activity as the parent molecule. Although GPR54 is a membrane-embedded protein, details of the molecular interaction between kisspeptin-10 and lipid membranes remain unclear. Here, we performed a series of structural analyses using alanine-scanning analogs of kisspeptin-10 in membrane-mimetic medium. We found that there is a close correlation between lipid membrane binding and agonist activity. For instance, the F10A and non-amidated (NH₂ → OH) analogs showed little or no GPR54-agonist activity and elicited no blue shift in tryptophan fluorescence. NMR analysis of kisspeptin-10 analog in DPC micelles revealed it to contain several tight turn structures, encompassing residues Trp3 to Phe10, but no helical conformation like that seen previously with SDS micelles. Together, our results suggest that kisspeptin-10 may activate GPR54 via a ligand transportation pathway incorporating a lipid membrane.